push starting & catalytic convertors

due to recent starter motor troubles I've been push starting my 2003 petrol engined car a lot. I know that push starting is bad for a catalytic convertor because of unburnt fuel entering it or something. I'm just wondering what is the likelihood of this happening as I've knowingly and stupidly been push starting it quite a lot. any idea's as to what damage i've done? to me i havent noticed any change in performance or am i just reducing the life of the catalytic convertor or is it going to take time for any side effects to show up? thanks

The engine really doesn't know the difference in being started from pushing it or via a starter motor. Why would any more unburned fuel be passed to the cat from push starting as opposed to crank starting? If anything the ECM might send more fuel via a wider injector pulse width when the key is turned to start. I could be wrong here, but I don't think you have anything to worry about.

^^^ ditto

thanks for your advice! But im still a bit worried as the hand book for the car also states my worry? :frown:

As long as the engine is starting right up when you pop the clutch you should be okay. The concern is in getting unburned fuel through the engine into the cat which will shorten its life. Realistically, even when key started, some unburned fuel does reach the cat during start, which is also the case during warm up before the O2 sensors reach temp and the fuel system goes into closed loop control. Again, this also happens during hard acceleration/heavy load, as the fuel system goes open loop during these conditions. Push starting where the engine is rotating but not starting, however, may indeed cause some problems.